Many varied advancements in technology have permitted the introduction, and popularization, of new types of communication systems as well as improvements to existing types of communication systems. Generally, in such new, as well as such improved, communication systems, the rates at which the data is transmitted, as well as the corresponding amount of data permitted to be communicated, has increased.
New types of, as well as improvements to existing, radio communication systems are exemplary of communication systems made possible as a result of advancements in communication technologies. Communication channels of a radio communication system are formed upon radio links, thereby obviating the need for conventional wireline connections to be formed between communication stations operable therein. Some radio communication systems, for instance, take advantage of the lack of wireline connections to form mobile communication systems in which one or more of the communication stations operable therein is capable of movement, not affixed in fixed positions.
Communication capacity of a communication system is sometimes limited due to bandwidth limitations. That is to say, the bandwidth capacity of the communication channel, or channels, available to the communication system to communicate data is sometimes limited. And, the limited capacity of the communication channel, or channels, limits the increase of the communication capacity of the communication system.
Communication channel bandwidth limitations are sometimes particularly acute in a radio communication system. Generally, a limited portion of the electromagnetic spectrum is allocated to a radio communication system upon which to define communication channels to communicate thereon. The communication capacity of the communication system is, many times, limited by such allocation. And, sometimes, the only manner by which to increase the communication capacity of the radio communication system is through more efficient use of the allocated spectrum.
The use of digital communication techniques permits the bandwidth efficiency of communications in the communication system to be increased. Use of such digital communication techniques is of particular advantage for use in a radio communication system due to the particular need efficiently to utilize the spectrum allocated thereto upon which to define communication channels thereon. Information that is to be communicated using digital communication techniques is digitized. The digitized information is formatted, such as into data packets, and the formatted data is communicated between communication stations. Individual ones, or groups, of the data packets can be communicated at discrete intervals and, once communicated, concatenated together to recreate the informational content of the digitized information.
As the data packets can be communicated at discrete intervals, a communication channel need not be dedicated for a single communication session between a pair of communication stations. Instead, the channel can be shared amongst a plurality of communication station-pairs to effectuate a plurality of separate communication sessions. Multiple increases in the communication capacity of a communication system are sometimes, thereby, provided.
Conventional LANs (local area networks) typically utilize a data packet protocol by which to communicate between nodes, i.e., communication stations, of the LANs. Wireless networks, operable in manners analogous to operation of conventional wired LANs, have also been developed and communicate data packets by way of communication channels defined upon a radio link, thereby to effectuate communications between communication stations.
A standard protocol promulgated by the IEEE (Institute of Electrical and Electronic Engineers), the 802.11 standard, sets forth the operational parameters of a wireless LAN.
Proposals have been set forth to utilize an unlicensed frequency band located at 5 GHz for WLANs. A variant of the 802.11 standard has also been promulgated for such WLANs.
Due to the unlicensed nature proposed of this 5 GHz frequency band, more than one WLAN might be installed over a common geographical area. And, other types of radio communication systems might also be installed over the same geographical area to operate, or to have frequency harmonics that have significant components at the 5 GHz band. Therefore, while the unstructured nature of an unlicensed band provides significant design freedom in the design of a communication system to be operable therein, the same unlicensed nature of the band also increases the possibility that signals generated during operation of one of the communication systems within the frequency band might generate signals that interfere with operation of another communication system operable at the same frequency band.
Use of frequency levels within the allocated band that exhibit lowest amounts of interference would best ensure that communication qualities of communications would not be degraded. Appropriate selection of the frequency levels is needed. And, subsequent reselection of the frequency levels is needed as communication conditions at the selected frequency level change.
The 802.11 standard sets forth system requirements for ad hoc networks, i.e., infrastructure-free networks of mobile stations (STAs). So, not only is there a need for dynamic frequency selection of the channel frequencies at which communication stations communicate data packets, but, also, the selection scheme must not be predicated upon use of a fixed control system.
A manner by which to provide for dynamic frequency selection in an ad hoc network of mobile stations is, therefore, needed.
It is in light of this background information related to communications in a radio communication system that the significant improvements of the present invention have evolved.
The present invention, accordingly, advantageously provides apparatus, and an associated method, for facilitating communications in a communication system that utilizes a dynamic frequency selection scheme. In a dynamic frequency selection scheme, the channel frequencies used to effectuate communication of data between communication stations operable therein are not set, but rather, are dynamically selected. A radio communication system to be operable pursuant to an IEEE 802.11 standard in the 5 GHz frequency band is exemplary of a communication system that utilizes a dynamic frequency selection scheme.
Through operation of an embodiment of the present invention, dynamic channel frequency selection pursuant to the dynamic frequency selection scheme is facilitated in an infrastructure-free, ad hoc network of communication stations. Any of the communication stations of the ad hoc network is able to select the channel frequencies to be used to effectuate communications.
In one aspect of the present invention, channel maps are maintained at each of the communication stations of the network. The channel maps contain channel characteristic indicia associated with communication conditions upon channels defined about various frequencies. When a communication station is designated as a DFS (dynamic frequency selection) owner, i.e., is placed in charge of the channel frequency selection, the indicia stored at the channel map is used in the channel frequency selection.
In another aspect of the present invention, measurements are made by one or more of the communication stations of channel conditions at different channel frequencies available to be used upon which to define communication channels. Measurements of the channel conditions at different channel frequencies is made at periodic, or other selected, intervals and is effectuated, for instance, by tuning a receive part of the communication station to the channel frequencies that might be available for selection upon which to communicate. Channel frequencies that appear to be used for communication, or other, operations are indicated as such and a channel characteristic indicia indicating the frequency unavailability is noted in the channel map of the communication station. When implemented at the unlicensed 5 GHz band, other communication systems might be using the channel frequency to communicate thereon, and, also, radar, and other, devices might also be operating at the measured channel frequencies. And, also, noise might also be exhibited at the channel frequencies. Indications of the noise level also are channel characteristics, indicia of which are stored at the channel map.
In another aspect of the present invention, channel map information created, or stored, at one communication station of the ad hoc network is communicated to others of the communication stations of the network.
In an implementation in which the ad hoc network is operable generally pursuant to the protocol set forth in the IEEE 802.11 standard, the channel map information is communicated between the communication stations (STAs) of the network during beacon periods defined therein on beacon signals sent between the communication stations. Each of the communication stations is able both to monitor channel frequencies to make determinations of conditions at the different channel frequencies and also to receive measurements made by others of the communication stations. The measurements made locally, and elsewhere, are averaged together and stored at the channel map of the communication station. Or, if the measured channel characteristic indicia at the communication station differs significantly from the values of the indicia measured elsewhere, the locally-measured indicia is inserted into the channel map of that communication station. As each communication station maintains a channel map of the channel characteristic indicia of various channel frequencies, any of the communication stations is able to become a DFS owner and to select the channel frequencies at which communication channels are defined and communications are effectuated between the stations of the ad hoc network. Change in the channel frequency at which the communications are effectuated are changed as necessary, best to ensure adequate communications between the communication stations of the ad hoc network.
When implemented in an ad hoc network of 802.11-compatible mobile stations, any of the mobile stations is capable of becoming the DFS owner, operable to define the channel frequency at which the communication channel is defined. Updating of the values of the channel characteristic indicia is made at selected intervals so that the channel map information is readily updated.
In these and other aspects, therefore, an assembly, and an associated method, is provided for a radio communication system formed of an ad hoc network of communication stations. Communications by the communication stations of the ad hoc network are effectuated upon dynamically-selected channel frequencies. Dynamic frequency selection of a channel frequency used by the communication stations of the ad hoc network to communicate thereon is facilitated. At least a first channel map is formed at least at a first communication station of the ad hoc network. The first channel map stores channel characteristic indicia associated with a first channel frequency and at least a second channel frequency. The channel characteristic indicia stored thereat is selectably used in the dynamic frequency selection of the channel frequency used by the communication stations to communicate thereon.
A more complete appreciation of the present invention and the scope thereof can be obtained from the accompanying drawings that are briefly summarized below, the following detailed description of the presently-preferred embodiments of the invention, and the appended claims.